Dummy medical instrument for use in a simulator

ABSTRACT

A dummy medical instrument for connection to a force feedback mechanism. The dummy medical instrument having a number of cables  5, 8  extending around control knobs  1, 2 . In a real instrument corresponding to the dummy instrument, the cables would extend to the tip of the instrument to allow controlled flexing of the tip of the instrument. In the dummy medical instrument, the same cables are routed down the umbilical of the instrument for connection to force feedback motors simulating the forces felt on the tip of the instrument.

The present invention relates to a dummy medical instrument for use in asimulator.

One type of simulator to which the present invention is applicable isthat disclosed in GB A 2252656. This simulator simulates the operationof an endoscopic process. A dummy endoscope is insertable into a fixturewhich is provided with a sensor mechanism to sense the longitudinal androtational movement of the dummy endoscope. This information is fed to acontroller which generates force feedback information based on virtualmodel data held in the computer memory. The force feedback applied tothe dummy endoscope is synchronised with a visual representation of theprocedure so as to provide a realistic simulation providing a usefultraining tool to endoscope users.

With an instrument such as an endoscope, the tip of the endoscope ismanipulated by angulation control in the form of one or more controlknobs on the handle of the endoscope which are linked to cables whichextend down the insertion tube of the endoscope. Turning of the controlknobs produces a corresponding movement of the cable and hence the tip.An endoscope can have two control knobs one of which controls theleft/right movement of the tip and the other of which controls theup/down movement of the tip.

According to the present invention there is provided a dummy medicalinstrument for use in a simulator, the instrument comprising a controlbody with user manipulatable angulation control, an insertion tube andan umbilical extending from the control body, wherein in a realinstrument corresponding to the one being simulated, at least oneangulation cable would extend from the user manipulatable controls tothe tip of the insertion tube such that movement of the angulationcontrol changes the angulation of the tip, and wherein in the dummymedical instrument the angulation cable extends from the usermanipulatable angulation control and down the umbilical to a device forcontrolling the resistance to movement of the cable to provide forcefeedback simulating the force which would be felt at the angulationcontrol of a real instrument.

With this arrangement, force feedback is provided to the angulationcontrol whilst using the angulation control and cable of the realinstrument (albeit with the cable being routed differently). This notonly provides a realistic feel, but also has the advantage that feweroriginal components need to be designed for the dummy instrument whichalso has benefits in terms of supplying users with replacement parts.

In the real instrument, the cables extend away from the angulationcontrol in the direction along the insertion tube. One option for thepresent invention is to reroute the cables completely so that theyextend away from the angulation control in the direction of theumbilical. However, the current preference is for the cable to extendaway from the angulation control towards the insertion tube as in thereal body, and to be turned back on itself to reroute it along theumbilical. There is limited space available in the control body, andthis approach provides the best way of routing the cables withoutinterfering with other components in the control body.

Within the constraints of the normal instrument, there is very littlespace available to turn the cable back on itself so that it is difficultto avoid generating undesirable friction which can distort the forcefeedback and cause premature wear of the cable. Therefore, preferablythe cable extends from the control body and around a pulley where it isturned through substantially 180° before being routed down theumbilical.

The use of the pulley eliminates sliding friction on the cable where itis turned back on itself. This provides not only smoother operation ofthe force feedback system, but also reduces the wear on the cable.

Preferably, the angulation cable is a co-axial cable in which a centralwire is moveable within a sleeve. The sleeve is preferably removed forthe portion of the cable surrounding the pulley, such that the wireengages directly with the pulley.

When more than one angulation cable is used, each cable should beprovided with its own pulley system. In one particularly advantageousarrangement, a first cable is wrapped around a single pulley, while asecond cable is wrapped around a pair of pulleys which are spaced apartso that the second cable forms a loop outside of the loop formed by thefirst cable.

In order to retain the cable on the pulley, the or each pulleypreferably has a convex periphery, and at least a part of the peripheryof the pulley is provided adjacent to the facing wall of a pulleyhousing.

An example of a dummy medical instrument constructed in accordance withthe present invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a plan view of the angulation system; and

FIG. 2 is a schematic perspective view showing the arrangement ofpulleys, cables and angulation control.

The particular medical instrument being described here is an endoscope.However, it may be any medical instrument where cables which arenormally manipulated to move a part of the instrument have to bererouted so that force feedback can be applied to the cable.

The described arrangement is adapted from a conventional endoscopecontrol body. Both of the real and dummy endoscopes have an insertionportion leading from the control body ending at the endoscope tip. Inthe real instrument, this tip is manipulated to steer it through thecolon. An umbilical is provided in both the real and dummy endoscopesleading from the control body to feed various cables to the controlbody.

The control body is provided with a pair of co-axial rotatable knobs 1,2as shown in FIG. 2. The outer knob 1, in this case, would, in a normalendoscope, be rotated to move the tip in an up/down direction, while theinner knob 2 would move the tip in a left/right direction orthogonal tothe up/down direction. These described directions are only notionaldirections as, in use, the endoscope may be used in any orientation.Wrapped around each pulley is a wire chain drive 3,4 to each of which acable is attached. In the illustrated example there are four cableswhich, for convenience, are denoted up cable 5, down cable 6, left cable7 and right cable 8.

In a normal instrument, these cables 5,6,7,8 would extend all the way tothe tip of the endoscope to provide the tip movement referred to aboveupon rotation of the knobs 1,2.

In the dummy instrument, these cables must be rerouted along theumbilical of the instrument which directs them to an angulation feedbackcontroller. In the angulation feedback controller, the up/down cables5,6 are connected to opposite sides of a force feedback motor and theleft/right cable 7,8 are connected to a similar motor.

Rotation of the knobs 1,2 is detected and a system controller interpretsthis information together with information on the longitudinal androtational positions of the tip of the endoscope. Using datarepresenting a simulated model of a colon, software detects when thesimulated tip of the endoscope comes into contact with the simulatedcolon wall. At this time, the controller sends a force feedback signalto the two feedback motors which hence provides a resistance to themovement of the cables 5–8 which is felt at the knobs 1,2 as aresistance to turning.

In order to route each cable into the umbilical 9, the arrangement shownin FIGS. 1 and 2 is employed. FIG. 1 shows the rerouting of two of thecables, namely the down cable 6 and the right cable 8. A similararrangement is provided on the opposite side of the control body asshown in FIG. 2. However, as this has the same construction andoperation as the down/right configuration shown in FIG. 1, only thisconfiguration is described in detail. The right cable 8 is connected tothe chain 4 that surrounds the inner knob 2. This cable then extendsaround a first pulley 10 rotatably mounted on a housing 11 within thecontrol body. The pulley 10 turns the right cable through 180°. A sheath12 is connected to the housing 11. The cable 8 enters the sheath 12 atthis point and is guided within this sheath into the umbilical whichleads it to the feedback motor.

The down cable 6 passes in a loop outside the right cable 8 around apair of spaced pulleys 13,14 rotatably mounted on the housing 11. Thedown cable 6 enters a sheath 15 attached to the housing 11 at connector16 and is also guided into the umbilical to the other force feedbackmotor as described with reference to the right cable.

1. A dummy medical instrument for use in a simulator, the instrumentcomprising a control body with a user manipulatable angulationcontroller, an insertion tube, and an umbilical extending from thecontrol body, wherein an angulation cable extends from the usermanipulatable angulation controller, and down the umbilical to a deviceadapted to control the resistance to movement of the cable to provideforce feedback simulating a force at the controller.
 2. An instrumentaccording to claim 1, wherein the cable extends from the control bodyand around a pulley where it is turned through substantially 180 °before being routed down the umbilical.
 3. An instrument according toclaim 1, wherein the angulation cable is a co-axial cable in which acentral wire is moveable within a sleeve.
 4. An instrument according toclaim 3, wherein the sleeve is removed for the portion of the cablesurrounding the pulley, such that the wire engages directly with thepulley.
 5. An instrument according to claim 1, wherein more than onecable is provided.
 6. An instrument according to claim 2, wherein morethan one cable is provided and each cable has its own pulley system. 7.An instrument according to claim 6, wherein a first cable is wrappedaround a single pulley, while a second cable is wrapped around a pair ofpulleys which are spaced apart so that the second cable forms a loopoutside of the loop formed by the first cable.
 8. An instrumentaccording to claim 2, wherein the pulley has a convex periphery, and atleast a part of the convex periphery of the pulley is provided adjacentto a facing wall of a pulley housing.